1. Field of the Invention
This invention relates to a device for inhibiting microorganism growth and, in particular, to a device useful to prevent fouling of primary sensing surfaces of analytical instruments.
2. Brief Statement of the Prior Art
Biochemical processes based on the activity of microorganisms frequently employ aqueous media which contain sediment and suspended solids, e.g., an activated sludge process which receives raw sewage streams containing sediment, suspended solids, oils, greases and the like. It is desirable to employ analytical instruments such as dissolved oxygen cells and the like directly in the process streams, thereby avoiding sampling errors inherently associated with streams of this nature.
It has been found that the primary sensor surfaces of analytical instruments when immersed in process streams of this nature rapidly become coated with a deposit of microorganism growth which causes erroneous readings of the instrument.
Various mechanical devices have been proposed for use in combination with analytical instruments such as dissolved oxygen cells, pH cells and the like. Typically these devices comprise agitators to stir the aqueous medium in the vicinity of the sensing surface such as illustrated by U.S. Pat. Nos. 3,498,889 or 3,878,049. Other techniques include apparatus for vibration of the analytical probe containing the oxygen sensing surface such as shown in U.S. Pat. No. 3,869,369. These devices are usually employed to insure that the vicinity of the sensing surface of the analytical probe is continuously replenished with fresh medium, thereby insuring a precise determination of the sensed variable such as dissolved oxygen and the like. When the analytical device is to be employed in a continuous process stream, stagnation of the liquid under analysis seldom occurs and these devices are not employed. The aforementioned devices do not prevent microorganism coatings on the sensing surfaces of process instruments even in rapidly flowing and agitated process streams.